QWebEngineDownloadItem's suggested filename might be wrong when contains special character

For example, in case of filename “foo bár test.txt” QWebEngineDownloadItem::path() returns “foo test.txt” for certain cases. Try the attached server example (web.py) with simplebrowser.

Steps to reproduce:

• Start web server: python web.py
• Start simplebrowser and connect to web server: ./simplebrowser localhost:8000
• Try links to check suggested filenames

Actual result:
When the server sends the filename in a http response header ( Content-Disposition: attachment; filename='foo b\xE1r test.txt' ) the word with accented character is dropped from filename:
“foo bár test.txt” -> “foo test.txt”

Expected result:
In all cases the suggested filename is “foo bár test.txt”.